1. Field of the Invention
The present invention relates to digital video interface, and more specifically, to a method for detecting the digital video interface off-line mode and associated receiver.
2. Description of the Prior Art
In general, the cathode ray tube (CRT) display is a stereotype of the analog video display device and the liquid crystal display (LCD) is a stereotype of the digital video display device. Meanwhile, the digital video display device is capable of receiving either analog video signals or digital video signals from a signal source such as a graphic card of the computer but eventually displays digital video signals on the screen.
A called “Digital Visual Interface (DVI)” standard, which has been announced by the Digital Display Working Group (DDWG), spreads a high-speed digital transmission technology for visual display signals. The digital video interface complied with the DVI standard is primarily focused on providing a higher compatible connection between a computer (e.g. workstation, desktop, laptop, etc.) and its different display devices (e.g. CRT, LCD, projector, etc.). In a digital video interface compliant host system, either a digital only interface or a combined analog and digital interface may be utilized.
As known, conventional host systems and liquid crystal displays all are inherently digital devices. The video interface for a CRT display requires a digital to analog converter (DAC) to convert the innate digital signal into the analog signal. However, a LCD may further require an analog to digital converter (ADC) for receiving and converting the analog video signal into the digital video signal. The requirements of DAC of the video interface and ADC of the liquid crystal display do not only result in increasing the cost but also degradation of the video quality during a plurality of conversions between the analog and digital signals.
Thus, the digital video interface provided with solutions of complete digital transmission becomes a popular video connection standard. Conventionally, a mode detection circuit is adopted to frequently detect the current mode of the video signals received by a transmission minimized differential signaling (TMDS) receiver. In a digital video interface system, Sync information is encoded in the data stream and TMDS receiver needs to use a receiver and decoder to decode the Sync information for mode detection. Even in off-line mode, without displaying any input image but monitoring the input signal, the prior art needs to turn on all TMDS receivers and decode the data continuously for mode detection. The full operation of all channels and the frequent detection of the conventional mode detection circuit causes high power consumption and heat dissipation.